I gave the car to my dad to bring to florida for a few months to use as a car down there while i foxed up their florida car they never use. After he made the 1300 mile trip down there with it he told me it was overheating. HE put some antifreeze in it after he said it was low, (he's 70 and not always right)

. My friend lives in the area and checked it out a month ago and it was hitting the 120 mark a few minutes after they started it. I finally made my way down here this week and cranked it up. I let it run for ten minutes and it ran fine, i drove it for about 20 minutes on the highway and side streets and it was 86 degrees out, I had the heat and AC on and the temp gauge was moving up and down but not above the 80C mark.
Any idea what this might be? I would love to bring it back to NYC to let me mechanic work on it but I'm scared of it heating up on the drive. I don't want to junk it as I've put too much money in it to get it running right the past two years.
We have owned it for about 5 years and it has 202k on it!
The water pump and coolant got changed about a 15 months ago as well but it wasn't by my mercedes mechanic since i didn't find him at that point yet.